ABSTRACT Disruption of the gut barrier has been implicated in the pathogenesis of multiple chronic illnesses that are characterized by chronic gastrointestinal inflammation. One such illness is inflammatory bowel disease (IBD), a complex, multi-factorial, autoimmune disorder of the gut in which diverse components (microbes, genetics, environment and immune response) intersect in elusive ways and culminate in overt disease 1. It is also heterogeneous with complex sub-disease phenotypes (i.e., strictures, fistula, abscesses, and colitis-associated cancers). Currently, patients are offered inflammation-reducing therapies that have only a ~30-40% response- rate, and 40% of responders become refractory to treatment within one year 2. Little to nothing has emerged that can fundamentally tackle the most widely recognized indicator/predictor of disease relapse, response and remission 3-8, i.e., a compromised epithelial barrier. Among the reasons cited are- 1) incomplete understanding of host-microbe interactions in the gut, and 2) our theoretical inability to pinpoint such a fundamental, actionable and effective target to drive a complex and nebulous process of gut barrier permeability. Preliminary studies using publicly available transcriptomic datasets from adult and pediatric patients with IBD and a set of unbiased novel computational approaches (Boolean implication relationships and Boolean Implication Networks) have pinpointed a novel target, whose activation is predicted to enhance a bona-fide barrier-protective pathway, and thereby, restore the gut barrier across the two subtypes of IBD, despite disease heterogeneity. Expression pharmacology studies using a companion biomarker in FFPE human tissues confirmed that the barrier-protective pathway orchestrated by this target is silenced in patients with IBD. Using a potent and highly specific drug that was previously developed for another indication and found to be safe in Phase I trials on healthy human adults, preliminary evidence has been obtained which shows that activation of the target is necessary and sufficient to trigger the barrier-protective pathway, and for the protection of the epithelial barrier in mice (chemical-induced colitis models) and in murine and human organoid-monolayers challenged with live microbes; it also restored the leaky gut barrier observed in IBD patient-derived organoids. This proposal seeks to validate the repurposing of this potent and specific drug for activating a novel barrier-protective target, the first of its kind, in the treatment of adult and pediatric IBD. Our specific Aims during the 3-y UG3 phase are all geared towards target validation: obtaining proof-of-mechanism in healthy murine and human colon-derived organoids (Aim 1); preclinical proof-of-principle studies using murine models of colitis (Aim 2); and expression pharmacology and proof-of-concept Phase `0' trials in patient-derived organoids (pediatric and adults; Aim 3). Successful demonstration of efficacy in UG3 phase will trigger the UH3-phase (Clinical trial planning; Aim 4). Although the focus here is on barrier-protective therapy to treat/prevent flares in IBD, network analysis revealed that the proposed therapeutic/indication pairing may also inhibit IBD-associated CRCs.